How to draw a NSString to UIView with every character is vertical

Question

I want to draw a NSString to UIView with every character is vertical,like this:

normal:

and after rotate:

i already have a solution:

- (void)drawTextInRect:(CGRect)rect {
for (int i = 0; i < self.text.length; i++) {
    NSString *subText = [self.text substringWithRange:NSMakeRange(i, 1)];

    CGContextRef context = UIGraphicsGetCurrentContext();

    CGContextSaveGState(context);


    // Create text
    CGContextSetFillColorWithColor(context, self.backgroundColor.CGColor);

    // Rotate the context 90 degrees (convert to radians)
    CGFloat rotate = (self.textDirection == MMLabelTextDirectionLeft)?(-M_PI_2):0;
    CGAffineTransform transform1 = CGAffineTransformMakeRotation(rotate);
    CGContextConcatCTM(context, transform1);

    // Move the context back into the view

    CGSize characterSize = [subText sizeWithAttributes:@{NSFontAttributeName:self.font}];

    CGContextTranslateCTM(context, -20, i*characterSize.height);

    // Draw the string
    [subText drawInRect:rect withAttributes:@{NSFontAttributeName:self.font}];
//        [subText drawAtPoint:CGPointMake(0, i*MAX(characterSize.width, characterSize.height)) withAttributes:@{NSFontAttributeName:self.font}];
    // Clean up

    CGContextRestoreGState(context);
}

}

My solution is not perfectly draw characters like 'r' or 'l',it makes me crazy!